The present invention is directed to a contactless communication system having a high bit rate contactless data transfer.
FIG. 7 illustrates a known contactless communication system 700. The basic components of contactless communication system 700 are reader 710 and contactless card 720.
Reader 710 is also known as a Proximity Coupling Device (PCD). Reader 710 includes generator voltage U0, transmission antenna LPCD, resonance capacitor Cres, and resistor RQ. Transmission antenna LPCD and resonance capacitor Cres are configured to be in resonance, such that at a predetermined frequency, only resistor RQ is seen from the perspective of the generator voltage U0.
Contactless card 720 is also known as a Proximity Integrated Circuit Chip (PICC), a smart card, a tag, a transponder, or a Radio Frequency Identification (RFID) tag. Contactless card 720 includes an inductive antenna LPICC, resonance capacitor CPICC, and energy consuming resistor RPICC. Antenna LPICC and resonance capacitor CPICC form a resonance circuit, and are configured to provide contactless card 720 with a specific resonance frequency.
In operation, transmission antenna LPCD transmits a carrier signal, typically having a frequency of 13.56 MHz, which generates a transmission field to supply the contactless card 720 with both energy and data. Data can be transmitted to contactless card 720 by modulation of the carrier signal. When contactless card 720 penetrates the transmission field of reader 710, the transmission field induces a current in card antenna LPICC, and the transmission antenna LPCD and card antenna LPICC are said to be coupled. A voltage corresponding to the induced current is then multiplied by the resonance circuit. In some implementations, contactless card 720 is configured to transmit a response signal, which is provided as the carrier signal with data modulated on a subcarrier frequency, typically at a frequency of 848 KHz. The response signal generates a response field that is detected by the transmission antenna LPCD of reader 710.
In known systems such as contactless system 700, the communication protocol between the reader and the contactless card may be defined by any of numerous ISO (International Organization for Standardization) standards, such as 14443 Type A/B, 18092, 15693, 18000, etc.
The data communication and energy supplied during downlink communication from the reader 710 to the contactless card 720 is accomplished with a single transmission antenna LPCD. To optimize energy transfer and operating distance, the reader's resonance circuit, comprising resonance capacitor Cres and transmission antenna LPCD, focuses on the carrier frequency and is often designed to have a high quality (Q) factor. The bandwidth is reciprocal to the Q factor, and thus the resulting bandwidth is low. Also, a high Q factor resonance circuit will attenuate the data-modulated carrier signal and affect the settling time of the signal. For standardized data rates (such as up to 848 kbit/sec), the downlink bandwidth of reader 710 is adequate to fulfill the transmission requirements. Higher data rates (such as above 848 kbit/sec) demand a larger bandwidth but without reduction of quality factor Q.